As an office PHS and a wireless LAN have been increasingly used in recent years, it has been crucial to create an electromagnetic wave environment in an office from the perspectives of preventing information leakage and also malfunction and noise due to externally intruding electromagnetic waves. There have been proposed various types of members for creating the electromagnetic wave environment in the office, or the like (e.g., Patent documents 1 and 2, etc.).
Patent document 1 discloses an electromagnetic shielding intelligent building in which information can be communicated with use of an electromagnetic wave having an arbitrary frequency in a wide frequency band by adding an electromagnetic shielding member such as metal or ferrite to a building frame. As the electromagnetic shielding member, there are disclosed electromagnetic wave reflectors such as a steel plate, metal net, metal mesh, and metal foil, and electromagnetic wave absorbers such as ferrite.
However, such electromagnetic wave reflectors and absorbers have no frequency selectivity. For this reason, the electromagnetic shielding intelligent building disclosed in Patent document 1 has a problem that because an electromagnetic wave having a specific frequency cannot be selectively shielded, electromagnetic waves other than that having the frequency to be shielded are also shielded.
On the other hand, Patent document 2 discloses an electromagnetic shielding building characterized in that an electromagnetic shielding space is ensured in the building with use of an electromagnetic shielding surface in which Y-shaped linear antennas are cyclically arrayed. The Y-shaped linear antenna is comprised of three segment-shaped elements radially extending from the center of the antenna by substantially the same length. Patent document 2 describes that the electromagnetic shielding building disclosed therein can select and electromagnetically shield an electromagnetic wave having an unnecessary frequency.    Patent document 1: Japanese Patent Publication No. 6-99972    Patent document 2: Japanese Unexamined Patent Application Publication No. 10-169039.Problems that the Invention is to Solve
In the electromagnetic shielding building described in Patent document 2, the linear antenna for reflecting the electromagnetic wave is formed in the Y-shape. In order to surely reflect the electromagnetic wave having the specific frequency, preferably the linear antennas are efficiently and densely arrayed on the electromagnetic shielding surface. However, regarding the Y-shaped antenna disclosed in Patent document 2, it is difficult to efficiently and densely arrange (many more linear antennas per unit area).
Also, in order to provide a high electromagnetic wave shielding property, it is particularly preferable that the elements are arranged so as to closely face to each other. However, regarding the Y-shaped antenna disclosed in Patent document 2, it is difficult to arrange the elements so as to make them face to each other in substantially parallel.
For this reason, the electromagnetic shielding building described in Patent document 2 has a problem that it is difficult to shield the electromagnetic wave having the specific frequency at a higher shielding ratio.
Also, a conventional electromagnetic screen has a large 10 dB bandwidth with respect to a matching frequency, so that electromagnetic waves having frequencies other than an intended specific frequency are also shielded. That is, the conventional electromagnetic screen has a problem of low frequency selectivity.
The present invention is made in consideration of such problems, and it is therefore an object of the present invention to provide an electromagnetic screen having a higher electromagnetic wave shielding ratio for an electromagnetic wave having a specific frequency.